Free cutting alloy



Patented Jan. 8, 1935 UNITED STATES PATENT OFFICE FREE CUTTING ALLOY William L. Fink, Oakmont, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. pplication September 18, 1933,

Serial No. 689,893

3 Claims. (01. 75-1) The invention relates to aluminum base alloys object is effected by the addition of from 0.05 and is particularly concerned with such alloys to about 1.5 per cent of cadmium to the aforecontaining copper, manganese and silicon. said aluminum-copper-manganese-silicon alloys.

An extensively used alloy of this nature con- I have found that cadmium is an alloying con- 6 tains from about 3.0 per cent to about 5.5 per stituent which has a very favorable effect on cent of copper, from about 0.25 per cent to about e mach ing pr s o a uminum a 1.5 per cent of manganese, and from about 0.25 alloys. 'In this specification and in the appended per cent to about 2.0 per cent of silicon, the claims, I use the term free machining w balance being commercial aluminum. This alloy applied to this constituent, to indicate this adl0 can be mechanically deformed by the well known vantageous effec on e i in pr p rti s, 10 commercial processes such as rolling, 'forging, as evidenced by the fact that the alloys containdrawing, or extrusion. The grain is thereby reing cadmium within the disclosed range may be lined and the physical properties considerably machined more p d y, With leSS o l Wear, less improved and suitable thermal treatments have l h rp n n better quality of p, d b r been devised to enhance the improvement. The ma hine Surf c h n Similar ll ys o n- 15 alloy has been used for many applications among tainin um. which-may be mentioned airplane propellers and A h h h mach-inability of h ys h r connectingrods for internal combustion engines. in disclosed y be i p y h a diti n There are, however, some applications wherein of f about to per cent Cadmium, I

the alloy might be conveniently and profitably prefer to use between about a pe 20 d were it t for a i herent; disadvantage cent of this element. A preferred composition which militates against its use in these applicawh h p fi s h p ys p t s f th tions. Mechanical cutting operations such as se oy n h improvement in machining drilling, shaping, or lathe-cutting are successq l y gained through the use of um is 25 fully carried out only by using certain precauan alloy containing about 4.4 p r cent of copper, 25 tions which increase the cost of production and 0-8 per cent of Silicon. 0. p c n of a an s perhaps favor the choice of another alloy which n 1 P cent f dm the b l being can be machined more readily but which is in substantially 1 luminum. other respects, for instance in physical prop- The addition of cadmium to the aluminumertles, not so desirable. When alloys are difficult p i on all ys of the class 30 to machine this disadvantage becomes evident hereinabove described not n y i pr ves the in many cases through rapid wear of the cutting machining characteristics but also effects an intool edge which necessitates frequent resharpencrease 111 the tensile Strength, Yi D m ehear ing. In such cases where machining is diflicult, Strength, e mell hardness values with a continual lubrication is required, the machined decrease m elongation t 35 surface is rough and irregular, and the chip has ture 15 0f Particular advantage in ppl oatlons a tendency to form continuous curlsor spirals Where an alloy must e m hin d that 1s m a that may foul the tool or the operating parts of thermally treated condition conducive to maxithe machine. The desirability is immediately mum t g hardness It thus posslble apparent of an alloy of good working characterto f high S.trength and satlsfactoi'y 3 40 istics, and outstanding physical properties, yet chmmg quahty m the same alloy combmatmn of properties heretofore diflicult to obtain. possessing favorable machining quahties so that The cadmium may be most conveniently added fimsh nachmmg opemmons may be performed by introducing it into the molten aluminum alloy eeonomlcally, successfully and may be produc' in solid metallic form since it melts at a point 45 tlve of Pleasmg Surface appearanceconsiderably below that of aluminum or its Accordingly an object of the invention is the alloys. It is desirable to keep the temperature Pr d i n f an alu a alloy e of the molten alloy below about 1400" F. to avoid ing from about 3.0 D c to about P r c t excessive volatilization of the cadmium. When 5 of copper, from about 0.25 per cent to about 1.5 once added, the melt should be vigorously stirred per cent of manganese and from about 0.25 per to insure a uniform mixture of the cadmium in cent to about 2.0 per cent of silicon which may be the alloy. readily and economically subjected to cutting The term aluminum used herein and in th operations appended claims, embraces the usual impurities My invention resides in the discovery that this found in aluminum ingot of commercial grade 2 7 1,988,828 v or picked up in the course of handling operations 2. An aluminum base alloy consisting of from incident to ordinary melting practice. about 3 to 5.5 per cent or copper, from about 0.25 The alloys herein disclosed may be subjected to 1.5 per cent of manganese, from about 0.25 to to the usual thermal treatments familiar to 2 per cent of silicon and from about 0.25 to 1.2

' 5 those skilled in the art for the purpose 01' imp r nt a a mi m, b l n m m- 5' proving or altering their physical characteristics. 3. An aluminum base alloy containing about. I claim: 4.4 per cent of copper, about 0.8 per cent oi. man- 1. An aluminum base alloy consisting of from ganflse, about P n f Sili on, nd a ou about 3 to 5.5 per cent of copper, from about 1 De? cent of cadmium; the balance being 10 0.25 to 1.5 per cent of manganese, from about aluminum. 10 0.25 to 2 per cent of silicon and from about 0.05 AM K- to 1.5 per cent of, cadmium, balance aluminum. 

